Novel Water Harvesting Fibrous Membranes with Directional Water Transport Capability

Previous studies about water harvesting from airborne moisture, which is driven by a directional water transport principle, are based on either a 2D surface or a 1D filament. Porous membranes with a directional water transport capability are seldom used for water harvesting. Herein, a novel hydrophobic/hydrophilic directional-wicking nanofibrous membrane is reported showing enhanced water harvesting ability. In comparison to the hydrophobic or hydrophilic membranes of the same structure and dimension, the directional wicking fibrous membranes have much higher water harvesting capacity. This fantastic water harvesting capability is originated from strong force to draw water from the hydrophobic to the superhydrophilic layer and ever permeable channels formed by the hydrophobic fibrous structure. Larger pores in the hydrophobic layer and smaller pores in the superhydrophilic layer facilitate water harvesting because of the enhanced directional wicking ability. The variation in pore dimension between the hydrophobic and the hydrophilic layers can result in 1.7 times difference in water harvesting capacity. These novel understandings may be useful for the development of advanced water harvesters for various applications.